Multi-destination relaying protocol for enhanced spectral efficiency

To improve the spectral efficiency of amplify-and-forward (AF) half-duplex relaying schemes, we propose a multidestination AF relaying protocol, in which the source sends two different data streams in two time-slots to two destinations with the aid of two relay nodes. In contrast to the conventional singledestination AF relaying protocol, the proposed multi-destination AF relaying protocol allows mutual interference in the transmission of the two data streams due to non-orthogonal resource allocation. Two relay nodes are opportunistically selected from a set of available relay nodes to maximize the minimum achievable rate of two data streams. We take into account the mutual interference and derive the ergodic capacity of the proposed protocol by deriving closed-form approximation. We show that the proposed protocol outperforms the conventional opportunistic AF relaying when the average power of interference is less than a crossover point and the proposed scheme has larger performance gain as the number of relay nodes increases in terms of the ergodic capacity.